Temperature-sensitive relay

Abstract

A temperature-sensitive relay is provided with a resilient, movable cantilever composed of amorphous ferromagnetic material having a Curie point. The cantilever is adapted to carry a first contact member. A second contact member is disposed adjacent the first contact member for at least intermittently establishing electrical contact with the first contact member. The relay is adapted to be connected to circuitry having a power source for providing an electrical current and a switching mechanism for activating the circuitry in response to a preselected condition. A magnet is associated with and adapted to bias the cantilever to a first position that interrupts electrical continuity between the first and second contact members. The cantilever is transformed from a ferromagnetic phase to a paramagnetic phase when its temperature exceeds the Curie point, whereby the cantilever assumes a second position in which the electrical continuity is established. A heating means is connected to the circuitry and disposed in the vicinity of the cantilever for heating the cantilever to effect the transformation during a preselected time interval following activation of the circuitry. The relay is lightweight, compact, economical to manufacture and reliable in operation.

We claim: 
     
       1. A temperature-sensitive relay adapted to be connected to circuit means having a power source for providing an electrical current and switching means for activating said circuit means in response to a preselected condition, said realy comprising: base means for mounting said temperature-sensitive relay;   a resilient movable cantilever carrying a first contact member, said cantilever being a composite member having a first portion composed of conductive material and a second portion composed of amorphous ferromagnetic material having a Curie point;   a second contact member disposed adjacent said first contact member for at least intermittently establishing electrical contact with said first contact member;   said first contact member being connected to first terminal means;   said second contact member being connected to second terminal means;   gripping means for supporting the cantilever and electrically connecting it to said first terminal means;   support means for supporting said second terminal means;   magnet means associated with and adapted to bias said cantilever to a first position that interrupts electrical continuity between said first and second contact members, said cantilever being transformed from a ferromagnetic phase to a paramagnetic phase when its temperature exceeds the Curie point, whereby said cantilever assumes a second position in which said electrical continuity is established;   heating means connected to said circuit means and disposed in the vicinity of said cantilever to effect said transformation during a preselected time interval following activation of said circuit means; and   bias means for urging said cantilever to move said first contact member to said second position.   
     
     
       2. A relay as recited in claim 1, wherein: said bias means includes a first portion of said cap member and a second portion of said base member, said first portion and said second portion entrapping a portion of said cantilever, and said first portion and said second portion being parallel to each other and disposed at an acute angle relative to said stationary contact member, thereby holding said entrapped cantilever portion at said acute angle to urge said resilient cantilever and said first contact toward said second position.   
     
     
       3. A relay as recited in claim 1, wherein: said bias means is a bent portion of said cantilever.   
     
     
       4. A relay as recited in claim 1, wherein: said bias means is a resilient means interposed between said base member and said cantilever.   
     
     
       5. A relay as recited in claim 1, wherein: said amorphous ferromagnetic material has a composition consisting essentially of Fe 33  Ni 40  Mo 4  B 11  Si 12 , subscripts being in atom percent.   
     
     
       6. A relay as recited in claim 1, wherein: said heating means is disposed in said base means.   
     
     
       7. A relay as recited in claim 1, wherein: said amorphous ferromagnetic material consists essentially of a composition defined by the formula M a  M' a  Z y , where M is at least one metal selected from the group consisting of Fe and Co; M' is at least one metal selected from the group consisting of Ni, Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta, W, Zn, Al and Cu, Z is at least one metalloid element selected from the group consisting of B, Si, C and P, x, a and y are in atomic percent and range from about 70-85, 0-12 and 15-30, respectively, and the sum of x+a+y equals 100.   
     
     
       8. A relay as recited in claim 1, further comprising means for connecting said relay to said circuit means to operate the electrical motor of a cooling fan for a vehicle radiator. 
     
     
       9. A relay as recited in claim 8, further comprises switch means disposed within the passenger compartment of said vehicle, said switch means being movable between an open position that interrupts electrical continuity between said power source and said heating means and a closed position that establishes electrical continuity between said power source and said heating means. 
     
     
       10. A relay as recited in claim 9, wherein said switch means comprises means for manual movement between said open and closed positions. 
     
     
       11. A realy as recited in claim 9, wherein said switch means, a comprises a second relay coupled thereto and movable from said open position to said closed position when temperature within said passenger compartment exceeds a preselected level. 
     
     
       12. A relay as recited in claim 1, wherein said magnet means is adpated to bias said cantilever to a first position that establishes electrical continuity between said first and second contact members, and wherein said cantilever is transformed from said ferromagnetic phase to said paramagnetic phase when its temperature exceeds the Curie point, whereby said cantilever assumes a second position in which said electrical continuity is interrupted.